Tranny Temp, MPG, etc

Jansen · February 12, 2005

Hello,

My average MPG is about 16 driving 60 miles a day split city and highway (70mph). I have the 5.3L V8, ext Cab 4x4. I hope this will increase during the summer but I don't know what to expect. I bought the truck on Dec/29/04.

I'm also curious about the tranny temp. I don't have a guage and wish I did. I have the towing package on the Z71 with the cooler. What do these trannys normally run? What would they be if they didn't have the tranny cooler?

Thanks for the help.

Jansen

AG Bill 05 Z71 · February 12, 2005

Regarding mileage, I average about 16.5 MPG for mixed highway/city driving also. I did have an interesting experience yesterday, however... I was driving on the freeway for about 200 miles, using Mobil gas, and averaging about 17.5 MPG going 70 MPH. I needed gas, and happened to stop where the only available gas was Shell gas. I filled up and immediately noticed my average MPG on the DIC went up to about 19.6 MPG driving the same speed and same terrain. The only change was the brand of gas....interesting..... I plan on refilling with my normal Mobil gas and see if the mileage goes back down..

On the tranmission oil temperature.... I just bought a new Escalade instrument cluster that I intend to install later today. The new cluster also includes a transmission temp gage that is red at 300 deg F. Since the trailer towing package includes a small external trans oil cooler in front of the radiator in addition to the cooler inside the radiator, I would expect the unloaded (no significant load or towing) trans oil temp to be in the 180 deg F range..... I will see how good my guess is after I install the new cluster..

AG Bill 05 Z71 · February 13, 2005

The Escalade instrument cluster install was completed without any problems. (See above post). I took it out for a test ride and the new trans temp gage stabilized at 125 deg F, a lot lower than my original guess of 180 deg F.

the blur · February 13, 2005

125 sounds about right. mine only hits 180 when I tow.

during the winter, mine will hardly budge at all.

obviously this is done by GM design.

however you will read all over the internet, trannys must be at least 160 to work properly. guess with the zillion trucks running cool tranny fluid, it's not a problem.

Jansen · February 13, 2005

Thanks for the info. Regarding Shell Gasoline. I've seen the increase in mpg as well. I had a jeep comanche and would routinely get 1 to 2 mpg better on shell. My previous truck (2004 F150 that I lemon Lawed) loved the shell too. I hadn't tried it in the GMC but now is a good time to start. Once, again thanks.

Jansen

AirForceAngler · February 13, 2005

Wow, I must have my foot in mine too much. I only get about 14 mpg with mixed city/highway. It's a 2000 5.3 Ext Cab Z71. 3:73 gears and 265/75R/16 tires.

About trans temp. In the winter running empty the needle hardly moves at all. In the summer empty it runs about 160/180. When I'm towing it gets to around 185/190. I tow a 27' camper trailer. Then I only get about 10 mpg!

toneman · February 14, 2005

Tranny temp on my Denali (no towing) is around 160-180 in city driving (e.g., more shifting), a bit higher during the hot summer months here in the Sacramento area. FWIW--during a trip to AZ last summer (also no towing), the tranny temp hit a smidge over 200 a few times, even at crusing speeds. Maybe the Westers might have something to do with it? I mention it because when I first got my Denali (and before Westers), the tranny temp would hardly go at most a couple of ticks past 100, no matter the driving pattern...although I think the fact that it was winter during that time may have had something to do with the "abnormally" low temps; I thought for a while there that maybe the tranny temp gauge was broken or something.